The present invention relates generally to the art of knitting, and more particularly, is directed to a circular type knitting machine which may be employed to knit a tubular fabric.
In the production of tubular knit fabrics, it has been the usual practice to employ circular knitting machines including a needle cylinder which is provided with a plurality of circumferentially spaced slots. Latch needles vertically reciprocate within the slots between stitch forming and latch clearing positions to produce a knitted fabric in accordance with a predetermined pattern. The circular cam is rotated relative to the needle cylinder and includes a cam track within which are positioned the butts of the knitting needles. Accordingly, as the cam is rotated upon operation of the machine, the interaction of the cam track and the knitting needle butts vertically reciprocates the knitting needles within the various needle cylinder slots in a known manner to produce a knitted tubular fabric.
The cam track of the prior art circular knitting machines circumferentially extends about the needle cylinder and generally follows an undulating path to thereby reciprocate the latch needles between their stitch forming and latch clearing positions. The cam track first raises the needle by engagement of the lower portion of the butt in the cam track and then lowers the needle to draw the stitch by engagement of the upper portion of the butt in the cam track. It has been found that if the angle between the needle and the normal to the cam track exceeds forty-five degrees, binding of the needle butts, excessive wear, and in many instances needle breakage occurs. This angle is usually referred to as the pressure angle. Due to the vertical orientation of the knitting needles and the angular orientation of the cam track, the prior art circular knitting machines have been designed for operation near the pressure angle. This design causes considerable friction at the cam track. The friction eventually results in wear sufficient to cause looseness or slap action of the needle latches and a decrease in machine component life due to wear.